The present invention relates to a suction roll having an internal suction box with improved noise damping. Suction rolls are used preferably in paper manufacturing machines, particularly to assist in removing water from the wet web of paper or board. One problem which has been encountered for decades is the disagreeable production of noise by such suction rolls. Numerous measures for reducing the noise produced by suction rolls have been described. See, for instance, the TAPPI journal, December 1956, Vol. 39, No. 12, pages 851 to 857.
Furthermore, U.S. Pat. No. 2,857,823 discloses placing a sound damping chamber along the discharge or circumferential outlet side of the stationary suction box. The inside of the sound damping chamber is connected by relatively fine openings with the inner surface of the shell of the suction roll and with the rest of the inside of the suction roll.
Known measures for reducing noise generated by a suction roll may be effective to a greater or lesser extent with machine operating speeds that are not too high. However, in modern paper manufacturing machines, with operating speeds of between 1000 and 2000 m/min, sound reduction techniques are insufficient. Traditional devices for reducing noise do not prevent production of a disagreeable noise by suction rolls operating at higher speeds.